If the material of the base of the casagrande liquid limit device on which the cup containing soil paste drop is softer than the standard hard rubber, then
According to IS classification the range of silt size particles is
1. Clay 200 mm
Highway Research Board (HRB) classification of soils is based on
HRB also known as public roads administrations (PRA) classification system. Based on both the particle size composition as well as the plasticity characteristics. Mostly used for pavement construction.
Inorganic soil with low compressibility are respectively by
a. MH – High Compressibility silt c. ML – Low Compressibility silt d. CH – High Compressibility clay
Sand particles are made of
Clay minerals 1. Kaolinite – China clay 2. illite - marine clays 3. Montmorillonite - high swelling/shrinking
The clay minerals with the largest swelling and shrinkage Characteristic is
Activity (A) = (Plasticity index) / (Percentage of clay particles) Activity indicates the present of clay minerals and the reaction with water. A 1.25 Active clay Montmorillonite(A>7) > illite > kaolinite Montmorillonite is present in black cotton soil.
Dispersed type of soil structure is an arrangement comprising particles having
Effective stress is
Effective stress or intergrannular stress is defined as the stress caused due to soil particles are coming close to the each other due to the distribution of the water. Its function of shear strength Effective stress is an abstract quantity, it cannot be measured directly in the laboratory. Pore water pressure can be measured by PIEZOMETER
Rise of water table above the ground surface causes
The total and effective stresses at a depth of 5m below the top level of water in a swimming pool are respectively
Total stress at depth of 5m below the top level of water, = Y. H = 1 × 5 = 5 kg/m² or 0.5kg/cm² Pore water pressure = Y. H = 1×5 = 5 kg/m² or 0.5 kg/cm² effective stress = Total stress - pore water pressure = 0.5 – 0.5 = 0
If the water table rises upto ground surface, then the
The critical hydraulic gradient (ic) of a soil mass of specific gravity G and voids ratio e is given by
The hydraulic gradient at which effective stress becomes zero is known as the critical hydraulic garedient. ic = Ysub/Yw. ic = (Gs–1) /(1+e)
Quick sand is a
When effective stress is zero then soil is said to be quick condition. If the critical gradient is exceeded the soil particles move upward, and the soil surface appears to be boiling. The quick condition is also known as boiling condition. Sand boiling happen in cohesionless soil such as fine sands and silt at a void ratio of 0.6 to 0.7
The hydraulic head that would produce a quick condition in a sand stratum of thickness 1.5m specific gravity 2.67 and void ratio 0.67 is equal
ic = h/L ic = G-1/1+e = 2.67-1/1+0.67 = 1. h/L = 1. so h = 1x1.5 = 1.5m
Physical properties of permeant which influence permeability are
Select the correct statement
Effective stress on soil
If the permeability of a soil is 0.8 mm/sec, the type of soil is
a. Clean gravel > 10 mm/sec b. Coarse and medium sand – 10^-2 to 10 mm/sec c. Fine sand, loose silt – 10^-4 to 0.01 mm/sec c. Dense silt, clayey silt 10^-5 to 1×10^-4 mm/sec d. Silt clay, Clay < 1×10^-5 mm/sec
Which of the following methods is most suitable for the determination of permeability of clayey soil
a. Constant head method - Coarse grain soil b. Variable or falling head method - Fine grain soil
Which of the following methods is best suited for determination of permeability of coarse grained soil
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